An Effective Field Theory for dark matter at a TeV-scale hadron collider should include contact interactions of dark matter with the partons, the Higgs and the Z. This note estimates the impact of including dark matter-Z interactions on the complementarity of spin dependent direct detection and LHC monojet searches for dark matter. The effect of the Z is small, because it interacts with quarks via small electroweak couplings, and the contact interaction self-consistency condition C/Λ2 < 4π/ŝ restricts the coupling to dark matter. In this note, the contact interactions between the Z and dark matter are parametrised by derivative operators; this is convenient at colliders because such interactions do not match onto low energy quark-dark matter contact interactions.

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Including the Z in an Effective Field Theory for dark matter at the LHC

Donald Glaser, 1960 Nobel laureate in Physics, recently passed away (2013), as have many of his colleagues who were involved with the early development of bubble chambers at the University of Michigan. In this paper I will review those early years and the subsequent wide-spread application of active-target (AT) bubble chambers that dominated high-energy physics (HEP) research for over thirty years. Some of the related, but more modern nuclear tracking detectors being used in HEP, neutrino astrophysics and dark-matter searches also will be discussed.

History of the bubble chamber and related active- and internal-target nuclear tracking detectors

It is generally accepted that dark matter must be found throughout galaxies. The observed motion of stars demands that galaxies contain large amounts of dark matter distributed throughout according to a particular density function. However, it is argued in this paper that this assumed density function should apply to all matter in the galaxy, not just dark matter. This paper reasons that in a region where a strong concentration of visible matter is observed, an absence of dark matter ought to be expected. In particular, calculations show that the dark matter density in the expanded solar neighbourhood (a kiloparsec radial extent from the Sun) should be as expected, in agreement with kinematic measurements; however, the immediate solar neighbourhood (within a few parsecs radial extent from the Sun) should be mostly devoid of dark matter, in accordance with the lack of success in finding dark matter using direct detection experiments on Earth.

Dark Matter Distribution in the Vicinity of Stars

PICASSO at SNOLAB searches primarily for spin-dependent WIMP interactions on 19F using the superheated droplet technique. This technique is based on the bubble chamber principle, where phase transitions in superheated liquid droplets can be triggered by WIMP induced nuclear recoils. The physics of the detection process allows a highly efficient suppression of backgrounds from cosmic muons, γ- and β-rays. We will discuss qualitatively recent progress in PICASSO and its sensitivity reach for spin-dependent and spin-independent WIMP searches.

R Podviyaniuk

Papers

Dark matter search with PICASSO